The present invention relates to a semiconductor thin film magnetic sensor and production method thereof.
Magnetic sensors, such as a magnetic resistance device or a Hall device, using a compound semiconductor thin film with a high electron mobility, such as InSb, are capable of detecting a static magnetic field, and are capable of detecting a rotational angle or speed even at a high or low rotational speed. Therefore, such sensors are widely used as magnetic sensors for small-sized DC motors.
However, InSb has a problem that it is difficult to meet the strict requirements of the recently expanding applications of magnetic sensors. For example, a magnetic sensor using InSb has a high sensitivity and exhibits very good characteristics in the vicinity of room temperature. However, since resistance of a magnetic sensing part greatly depends on temperature, at low temperatures of, below xe2x88x9240xc2x0 C., a magnetic sensor using InSb becomes liable to pick up electrical noises due to considerable increase in resistance of the device. Further, at high temperatures exceeding 120xc2x0 C. increases in drive current because of a large decrease in device resistance results in driving difficulty. That is, InSb has a maximum temperature variation rate of resistance of xe2x88x922%/xc2x0 C., thus having a high temperature dependence. The temperature variation rate xcex2R of resistance is determined by the following equation:
Temperature variation rate xcex2R (%/xc2x0 C.)=(1/R)dR/dTxc3x97100.
In the present invention, a small temperature variation of resistance generally means a small value of the temperature variation rate xcex2R (%/xc2x0 C.).
Recently, magnetic sensors are widely used as non-contact sensors, and the application fields of such sensors is expanding. In such the recently expanding application field of magnetic sensors, as compared with prior art applications, requirements are increasing for using magnetic sensors as non-contact sensors even under conditions of lower temperatures or higher temperatures. In general, the temperature range at which the magnetic sensor is driven tends to be expanding. In the application of small-sized motors used in the conventional VTR or personal computers, the magnetic sensor has been sufficient if it is usable in a temperature range in the vicinity of room temperature, for example, in the range of about xe2x88x9220 to 80xc2x0 C. (drive temperature range of substantially 100xc2x0 C.). However, in a non-contact magnetic sensor for an automobile or an industrial non-contact magnetic sensor which is expected to be expanding in demand, use in the temperature range of xe2x88x9250xc2x0 C. to 150xc2x0 C. (drive temperature range of substantially 200xc2x0 C.) is actually required.
Because InSb has a high temperature dependence with a temperature variation rate that is negative, an InSb sensor has a high resistance at a low temperature, and a low resistance at a high temperature. If the temperature changes from xe2x88x9250xc2x0 C. to +150xc2x0 C., resistance at xe2x88x9250xc2x0 C. is 28 to 30 times (54 times when the temperature variation rate of resistance is xe2x88x922%) as high as resistance at +150xc2x0 C. As a result, variation of self resistance in effect becomes a variation of input resistance of the magnetic sensor, and as a result, at high temperatures, a breakdown or the like due to eddy current is generated, a higher drive input current becomes required, and in a small-sized integrated drive circuit, stable drive of the device becomes difficult. That is, a complex, expensive drive circuit is required.
Further, at low temperatures, device resistance becomes very high, which results in a strong influence of stray magnetic noise or causes misoperation due to noise As a result, the magnetic sensor is usable only in very limited cases, and its merit as a non-contact sensor, hasp not been sufficiently utilized.
When such a magnetic sensor, a power supply for driving the magnetic sensor, and a control circuit of the magnetic sensor for amplifying the magnetic field detection output are attempted to be realized in a small size, at a low cost, and with high performance, such a temperature dependence of resistance due to the material is a great problem. For example, a maximum ratio of resistance at xe2x88x9250xc2x0 C. and resistance at 150xc2x0 C. must be within 15 times in absolute value.
The present invention has been made for solving the above-described problems of the prior art magnetic sensors, and an object of the present invention is to provide a magnetic sensor that is capable of operating with a simple drive circuit with a high sensitivity, a small temperature dependence, and in a wide temperature range. A further object of the present invention is to provide a magnetic sensor that is capable of being driven in the range of xe2x88x9250xc2x0 C. to 150xc2x0 C. with high reliability and capable of being driven by a small-sized, low-cost control circuit. More specifically, an object of the present invention is to provide a high sensitivity, high reliability magnetic sensor that is small in change of input resistance of the magnetic sensor between a low temperature (for example, xe2x88x9250xc2x0 C. which is a required lower limit temperature) and a high temperature (for example, 150xc2x0 C. which is a required higher limit temperature).
Further, in driving the magnetic sensor in a wide temperature range from low to high temperatures, a large thermal stress is exerted through a package of the magnetic sensor, and a passivation technology for protecting the magnetic sensing part from a new thermal stress is necessary, and meeting such a requirement is also an object of the present invention.
The inventors have investigated composition, thin film formation, doping and the like of a compound semiconductor thin film having a high electron mobility which is capable of producing a high sensitivity magnetic sensor and also investigated matching with a control circuit. In particular, as a result of investigating temperature dependence of device resistance or device resistance change at low and high temperatures, a thin film with a high electron mobility capable of suppressing temperature variation of input resistance of the magnetic sensor to a small value and a production method thereof have been found. As a result, the inventors have found a magnetic sensor with a small temperature variation of resistance.
Further, in driving the magnetic sensor in a wide temperature range from low to high temperatures, a large thermal stress is exerted through a package of the magnetic sensor. However, by forming on the magnetic sensing part an intermediate layer of a dielectric III-V group compound semiconductor having the same properties as III-V group compound semiconductor constituting the magnetic sensing part, a passivation technology for protecting the magnetic sensing part from thermal stress is exerted directly from the inorganic passivation layer (protective layer). As a result, a magnetic sensor structure capable of driving in a wide temperature range and with a high reliability has been found.
Further, it has been found that when temperature variation of input resistance of the magnetic sensor is within a predetermined range, the sensor can be driven by a small-sized control circuit in a wide temperature range.
Still further, a small-sized digital output magnetic sensor apparatus and a production method thereof have been found, which magnetic sensor apparatus combines a high sensitivity magnetic sensor as a magnetic sensing part using a compound semiconductor thin film providing a high mobility satisfying such requirement, with a small-sized control circuit for such a magnetic sensor, which is capable of outputting an output proportional to magnetic field detection signal and a plurality of signals corresponding to detection or non-detection of magnetic field
That is, a magnetic sensor according to the teachings of the present invention comprises a magnetic sensor having an InxGa1xe2x88x92xAsySb1xe2x88x92y (0 less than xxe2x89xa61, 0xe2x89xa6yxe2x89xa61) thin film layer formed on a substrate as an operation layer of the magnetic sensing part, characterized in that the thin film layer contains at least one type of donor atom selected from the group consisting of Si, Te, S, Sn, Ge and Se.
The magnetic sensor according to a second of the present invention is characterized in that in the magnetic sensor described above, at least part of the donor atom is positively ionized for supplying conduction electrons into the operation layer of the magnetic sensing part. Here, more specifically, the donor atom, at least part thereof is positively ionized by substituting any one atom of InGaAsSb at a lattice point of crystal.
The magnetic sensor according to third aspect of the present invention is characterized in that in the magnetic sensor of described above, the thin film layer has an electron concentration of 2.1xc3x971016/cm3 or more, and an electron mobility xcexc (cm2/V.s) and the electron concentration n (1/cmxe2x88x923) of the thin film layer have a relation of
Log10(n)+4.5xc3x9710xe2x88x925xc3x97xcexcxe2x89xa717.3
Here, the electron mobility is more preferably greater than 6000 cm2/V.s. By setting the electron mobility xcexc and the electron concentration n in such ranges, a high sensitivity, small temperature dependence magnetic sensor can be produced. When a magnetic sensor of even higher sensitivity is to be produced, the electron mobility is preferably greater than 10000 cm2/V.s.
The magnetic sensor according to a fourth aspect of the present invention is characterized in that in the magnetic sensor described above, the thin film layer has an electron mobility of 6000 cm2/V.s or more.
The magnetic sensor according to a fifth aspect of the present invention is characterized in that in the magnetic sensor of the above-described first and second aspects, the thin film layer has an electron concentration of 2.1xc3x971016/cm3 or more, and an electron mobility xcexc (cm2/V.s) and the electron concentration n (1/cmxe2x88x923) of the thin film layer have a relation of:
Log10(n)+4.5xc3x9710xe2x88x925xc3x97xcexcxe2x89xa718.0
The magnetic sensor according to a sixth aspect of the present invention is characterized in that in the magnetic sensor of the fifth aspect described above, the thin film layer has an electron mobility of 10,000 cm2/V.s or more.
Here, for achieving high sensitivity and small temperature dependence magnetic sensor operation, the electron mobility xcexc is preferably greater than 15,000 cm2/V.s, and even more preferably greater than 20,000 cm2/V.s.
The magnetic sensor according to a seventh aspect of the present invention is characterized in that in the magnetic sensor of the above-described a sixth aspect, the thin film layer is an InAsySb1xe2x88x92y (0xe2x89xa6yxe2x89xa61) thin film layer.
The magnetic sensor according to an eighth aspect of the present invention is characterized in that in the magnetic sensor of the above-described aspects, the thin film layer is an InSb thin film layer.
The magnetic sensor according to a ninth aspect of the present invention is characterized in that in the magnetic sensor of any one of the above-described aspects, the surface of the substrate comprises a dielectric III-V group compound semiconductor.
The magnetic sensor according to a tenth aspect of the present invention is characterized in that in the magnetic sensor of any one of the above-described aspects, the substrate comprises a dielectric GaAs single crystal.
The magnetic sensor according to an eleventh aspect of the present invention is characterized in that in the magnetic sensor of any one of the above-described aspects, the thickness of the operation layer is 6 microns or less.
The magnetic sensor according to a twelfth aspect of the present invention is characterized in that in the magnetic sensor of any one of the above-described first to tenth aspects, the thickness of the operation layer is 0.7 to 1.2 microns.
The magnetic sensor according to a thirteenth aspect of the present invention is characterized in that in the magnetic sensor of any one of the above-described first to tenth aspects, the thickness of the operation layer is 1.2 microns or less.
The magnetic sensor according to a fourteenth aspect of the present invention is characterized in that in the magnetic sensor of any one of the above-described first to thirteenth aspects, the magnetic sensor is a Hall device. In this Hall device, a preferable thickness of the operation layer is 1.2 microns or less, or 0.5 microns or less, when a Hall device of even higher input resistance and reduced power consumption is produced, and 0.1 microns or less, or even more preferably 0.06 microns or less.
The magnetic sensor according to a fifteenth aspect of the present invention is characterized in that in the magnetic sensor of any one of the above-described first to thirteenth aspects, the magnetic sensor is a magnetic resistance device. In the such a magnetic resistance device, a preferable thickness of the operation layer is 1.2 microns or less, or 0.5 microns or less, when a device of even higher input resistance and reduced power consumption is produced, and even more preferably 0.2 microns or less.
Further, sixteenth aspect of the present invention discloses a semiconductor magnetic resistance apparatus, the apparatus comprises four device parts comprising semiconductor thin films for generating a magnetic resistance effect, a wiring part, and a bonding electrode on a flat substrate surface, the four magnetic resistance effect generating device parts are connected in a bridge structure, and of the four device parts, two devices at opposite sides of the bridge structure are disposed so as to be applied perpendicularly with magnetic fields of the same strength. The device parts and the bonding electrode are connected by the wiring part.
The semiconductor magnetic resistance apparatus according to a seventeenth aspect of the present invention is characterized in that in the apparatus of the above-described sixteenth aspect, the wiring part does not cross.
The semiconductor magnetic resistance apparatus according to an eighteenth aspect of the present invention is characterized in that in the apparatus of the above-described sixteenth or seventeenth aspects, resistances of the wiring parts from the connection point connecting the four device parts to the bonding electrodes are equal to each other.
Further, a nineteenth aspect of the present invention discloses a magnetic sensor apparatus, with the magnetic sensor apparatus packaging a magnetic sensor, an amplifier circuit for amplifying an output of the magnetic sensor, a magnetic circuit having a power supply circuit for driving the magnetic sensor, the apparatus being characterized in that the magnetic sensor is a magnetic sensor as described in any one of the above-described first to eighteenth aspects of the invention.
The magnetic sensor apparatus of a twentieth aspect of the present invention is characterized in that in the magnetic sensor apparatus of the above-described nineteenth aspect, input resistance of the magnetic sensor at xe2x88x9250xc2x0 C. is set to within 15 times the input resistance at 150xc2x0 C.
The magnetic sensor apparatus of a twenty first aspect of the present invention is characterized in that in the magnetic sensor apparatus of above-described nineteenth or twentieth aspects, the output after being amplified by the amplifier circuit is proportional to the output of the magnetic sensor.
The magnetic sensor apparatus of a twenty second aspect of the present invention is characterized in that in the magnetic sensor apparatus of the above-described nineteenth or twentieth aspects, the output after being amplified by the amplifier is a digital signal output corresponding to the detection and/or non-detection of a magnetic field by the magnetic sensor.
Further, a twenty third aspect of the present invention discloses a production method of the magnetic sensor, the production method is characterized by comprising a process for forming an InxGa1xe2x88x92xAsySb1xe2x88x92y (0 less than xxe2x89xa61, 0xe2x89xa6yxe2x89xa61) thin film having an electron concentration of 2xc3x971016/cm3or more on a substrate, a process for forming the thin film into a desired pattern, a process for forming a plurality of thin metal thin films on the thin film, and a process for connecting a plurality of external connection electrodes to an end of the thin film.
The production method of a twenty fourth aspect of the present invention is characterized in that in the production method of magnetic sensor of the above-described twenty third aspect, the process for forming the InxGa1xe2x88x92xAsySb1xe2x88x92y (0 less than xxe2x89xa61, 0xe2x89xa6yxe2x89xa61) thin film further comprises a process for containing at least one type of donor atom selected from the group consisting of Si, Te. S, Sn, Ge and Se in the thin film.
Further, a twenty fifth aspect of the present invention discloses a production method of the magnetic sensor, the production method is characterized by comprising a process for packaging a circuit for amplifying a magnetic field detection signal of the magnetic sensor and a control circuit having a power supply circuit for driving the magnetic sensor, wherein the magnetic sensor is a magnetic sensor as described in any one of the above-described first to eighteenth aspects of the invention, and the magnetic sensor is produced by the production method as described in the above-described twenty third and twenty fourth aspects.
Further, a twenty sixth aspect of the present invention discloses a magnetic sensor of another construction, the magnetic sensor is characterized as comprising a substrate, an operation layer including an InxGa1xe2x88x92xAsySb1xe2x88x92y (0 less than xxe2x89xa60, 1xe2x89xa6yxe2x89xa61) thin film layer formed on the substrate, a dielectric or high resistance semiconductor intermediate layer formed on the operation layer, and a dielectric inorganic protective layer (that is, a passivation layer), stacked in the above order.
The magnetic sensor of a twenty seventh aspect of the present invention is characterized in that in the magnetic sensor of the above-described twenty sixth aspect, the intermediate layer contacts the operation layer and has a lattice constant approximate to the lattice constant of the operation layer.
The magnetic sensor of a twenty eighth aspect of the present invention is characterized in that in the magnetic sensor of the above-described twenty seventh aspect, the intermediate layer has a composition containing at least one element elected from the elements constituting the InxGa1xe2x88x92xAsySb1xe2x88x92y (0 less than xxe2x89xa61, 0xe2x89xa6yxe2x89xa61) thin film.
The magnetic sensor of a twenty ninth aspect of the present invention is characterized in that in the magnetic sensor of the above-described twenty seventh aspect, the operation layer has a barrier layer on the InxGa1xe2x88x92xAsySb1xe2x88x92y (0 less than xxe2x89xa61, 0xe2x89xa6yxe2x89xa61) thin film.
The magnetic sensor of a thirtieth aspect of the present invention is characterized in that in the magnetic sensor of the above-described twenty ninth aspect, the intermediate layer has a composition containing at least one elements selected from the elements constituting the barrier layer.
The magnetic sensor of a thirty first aspect of the present invention is characterized in that in the magnetic sensor of any one of the above-described twenty seventh to thirtieth aspects, the InxGa1xe2x88x92xAsySb1xe2x88x92y (0 less than xxe2x89xa60xe2x89xa6yxe2x89xa61) thin film contains at least one type of donor atom selected from the group consisting of Si, Te, S, Sn, Ge and Se.
The magnetic sensor of a thirty second aspect of the present invention is characterized in that in the magnetic sensor of the above-described thirty first aspect, at least part of the donor atom is positively ionized for supplying conduction electron into the operation layer. Here, more specifically, it is characterized in that the donor atom, at least part thereof, is positively ionized by substituting any one atom of InGaAsSb at a lattice point of the crystal.
The magnetic sensor of a thirty third aspect of the present invention is characterized in that in the magnetic sensor of any one of the above-described twenty seventh to thirty first aspects, the intermediate layer contains at least one type of donor atom selected from the group consisting of Si, Te, S, Sn, Ge and Se.
The magnetic sensor of a thirty fourth aspect of the present invention is characterized in that in the magnetic sensor of any one of the above-described twenty seventh to thirty third aspects, the InxGa1xe2x88x92xAsySb1xe2x88x92y (0 less than xxe2x89xa61, 0xe2x89xa6yxe2x89xa61) thin film has a resistance of the thin film at xe2x88x9250xc2x0 C. within 15 times the resistance at 150xc2x0 C.
Further, a thirty fifth aspect of the present invention discloses a magnetic sensor apparatus of another construction, the apparatus integrally packages a magnetic sensor, a circuit for amplifying an output of the magnetic sensor, a control circuit having a power supply circuit for driving the magnetic sensor, characterized in that the magnetic sensor is a thin film magnetic sensor as described in any one of the above-described twenty seventh to thirty fourth aspects of the invention.
Further, a thirty sixth aspect of the present invention discloses a production method of a magnetic sensor of another construction, the production method is characterized by comprising a process for forming an InxGa1xe2x88x92xAsySb1xe2x88x92y (0 less than xxe2x89xa61, 0xe2x89xa6yxe2x89xa61) thin film on a flat surface substrate, a process for forming an intermediate layer of a compound semiconductor of approximate physical properties to the thin film on the thin film, a process for forming the thin film and the intermediate layer into a desired pattern, a process for forming a thin metal film of a desired shape on the formed pattern, a process for forming a dielectric inorganic protective layer on the pattern and the metal thin film, a process for forming a plurality of electrodes for external connection, and a process for connecting the electrodes to an end of thee InxGa1xe2x88x92xAsySb1xe2x88x92y (0 less than xxe2x89xa61, 0xe2x89xa6yxe2x89xa61) thin film.
Further, a thirty seventh aspect of the present invention discloses a production method of a magnetic sensor of yet further construction, the production method is characterized by comprising a process for forming an InxGa1xe2x88x92xAsySb1xe2x88x92y (0 less than xxe2x89xa61, 0xe2x89xa6yxe2x89xa61) thin film on a flat surface substrate a process for forming a barrier layer, a process for forming an intermediate layer of a compound semiconductor of approximate physical properties to the barrier layer on the barrier layer, a process for forming the thin film, the barrier layer and the intermediate layer into a desired pattern, a process for forming a thin metal film of a desired shape on the formed pattern, a process for forming a dielectric inorganic protective layer on the pattern and the metal thin film, a process for forming a plurality of electrodes for external connection, and a process for connecting the electrodes to an end of the InxGa1xe2x88x92xAsySb1xe2x88x92y (0 less than xxe2x89xa61, 0xe2x89xa6yxe2x89xa61) thin film.